Tooth model for dentistry practical training

ABSTRACT

A tooth model for dentistry practical training capable of correct shape measurement using laser light is disclosed.  
     The tooth model for dentistry practical training having a tooth crown portion  1  formed as an imitation of the shape of a tooth is characterized that at least the tooth crown portion  1  is made of a tooth crown portion forming material having non-transparency or semi-transparency, a center-line average roughness Ra of the surface of the tooth crown portion  1  is 0.1 μm or more and less than 10 μm, and a light reflectance of the surface of the tooth crown portion  1  is 70% or higher for light of 700 nm in wavelength. The color difference ΔE*ab from a standard white color of the tooth crown portion forming material is 15 or less. Since the shape of the tooth crown portion can be correctly measured by a non-contact, high speed, three-dimensional shape measuring instrument, by using this tooth model, results of various kinds of a treatment practice and a preparation practice can be correctly evaluated in the educational field.

TECHNICAL FIELD

The present invention relates to a tooth model for dentistry practicaltraining, and particularly, to a tooth model for dentistry practicaltraining capable of correct shape measurement using laser light.

BACKGROUND ART

Tooth models for dentistry practical training have been conventionallyemployed widely in the educational field including a dental collage, adental technician training school and the like, and as one example ofsuch a tooth model for dentistry training, for example, Japanese PatentPublication No. 2506212 discloses a denture that can be easily mountableinto or demountable from a tooth placing site of a alveolar model usingan elasticity of a leaf spring, and Japanese Laid-Open PatentPublication No. 2002-628 discloses an tooth models having a structure inwhich a protrusion fitting in a recess formed in the a alveolar modelside is provided to a tooth root portion.

In various educational facilities, shape measurement using laser lighthas been on the way to a practical use on a tooth model after apreparation practice or an endodontic treatment practice (fillingpractice) in order to evaluate results of such treatment practices usinga tooth model, whereas in a case of a general plastic tooth modeldescribed in the above publications, a glossiness of the surface of atooth, when being illuminated with laser light, is too large to causescattering of laser light at a proper level, thereby disabling correctshape measurement of a tooth using laser light to be conducted.

The object of the present invention is to provide a tooth model fordentistry training capable of correct shape measurement using laserlight in order to solve the problem.

DISCLOSURE OF THE INVENTION

A tooth model for dentistry training of the present invention has atooth crown portion formed as an imitation of the shape of a tooth,wherein the tooth crown portion is made of at least a tooth crownportion forming material having non-transparency or semi-transparency, acenter-line average roughness Ra of the surface of the tooth crownportion is 0.1 μm or more and less than 10 μm and a light reflectance ofthe surface of the tooth crown portion is 70% or higher for light of 700nm in wavelength.

A tooth model for dentistry training of the present invention is thetooth model having the features, wherein a color difference ΔE*ab from astandard white color of the tooth crown portion forming material is 15or less.

BRIEF DESCRIPTION THE DRAWING

FIG. 1 is a view showing an example of a schematic shape of a toothmodel for dentistry training of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Description will be given of the present invention showing an example ofa schematic shape of a tooth model for dentistry training of the presentinvention in FIG. 1.

A tooth model for dentistry training of the present invention, as shownin FIG. 1, has a tooth crown portion 1 formed artificially as animitation of a human tooth and the tooth crown portion 1 is of a singlelayer structure or a multilayer structure. That is, the tooth crownportion 1 of the tooth model of the present invention may be of amultilayer structure having an enamel layer on the surface thereof, asin an actual tooth (a natural tooth), and an dentin in the interior, oralternatively may be of a single layer structure in which the enamellayer and the dentin are formed from the same material. A pulp cavitymay be formed in the interior of the dentin, and, as exemplified in FIG.1, the tooth crown portion 1 is preferably connected to the tooth rootportion 2 so as to be capable of installment in a prescribed alveolarmodel.

In a tooth model of the present invention, the tooth crown portion 1 ismade of at least a tooth crown forming material having non-transparencyor semi-transparency and the tooth crown portion 1 has fine concavityand convexity in the surface thereof. With a surface profile havingexcessively smaller peak and valley height and roughness spacing of thetooth crown portion 1, no scattering of laser light in shape measurementusing laser light is caused in reflection of the laser light in shapemeasurement on the surface of the tooth crown portion 1 to therebydisable shape measurement of the tooth model, which is because thesurface of the tooth crown portion has many of inclined surfacesrelative to a laser light oscillator and laser light reflected on thesurface of the tooth crown portion is propagated in a directiondifferent from that toward a laser light receiving section. To thecontrary, with a surface profile having excessively larger peak andvalley height and roughness spacing of the tooth crown portion 1, asurface shape of the tooth model is altered in a way such that a goodresult cannot be obtained in shape measurement using laser light.

In the present invention, it is necessary for a center-line averageroughness Ra to be generally 0.1 μm or more and less than 10 μm anddesirably 0.15 μm or more and less than 5 μm and a better shapemeasurement result can be obtained by adjusting the center-line averageroughness within in the ranges.

A surface roughness defined in the present invention is one measuredaccording to JIS B 0601-1982, and defined as a center-line averageroughness Ra is the average value of results of measurement on theflattest possible surface of a tooth crown portion obtained at any siteand in any direction therein three times, respectively. Note thatmeasurement of a surface roughness is conducted respectively at any sitemeasured in a tooth crown portion in conditions of a measuring length of0.5 mm, a measuring speed of 0.03 mm/sec and a cut-off value of 0.08 mm.

In the present invention, when a light reflectance of the surface of atooth crown portion is low, reflecting light of laser light to be usedfor measurement is weak to thereby disable a good measurement result tobe obtained, which requires a light reflectance of the surface of atooth crown portion of 70% or more for light of 700 nm in wavelength.The term, a light reflectance, herein means a reflectance includingdirect reflection according to JIS Z 8722-1982. In the presentinvention, a light reflectance is defined as the average value ofresults of measurement on the flattest possible surface of a tooth crownportion obtained at any site therein three times.

In the present invention, in order to obtain a light reflectance of thesurface of a tooth model of 70% or more, it is necessary for a materialof the surface of a tooth crown portion to have non-transparency orsemi-transparency. That is, when a material of which a tooth crownportion is made has non-transparency or semi-transparency, there can beobtained a comparatively high light reflectance value, whereas if amaterial of which a tooth crown portion is made has transparency, alight quantity transmitted through the material increases and thereby alight reflectance is lower, leading to a measurement data deficientarea.

As materials of the surface of a tooth crown portion of a tooth model ofthe present invention (a tooth crown portion forming material), therecan be employed generally known ones, which are exemplified as follows:porcelain such as ceramics and the like; thermoplastic resin materialssuch as acrylate, polystyrene, polycarbonate,acrylonitrile-styrene-butadiene copolymer (ABS), polypropylene,polyethylene, polyester and the like; and thermoset resin materials suchas melamine, urea, unsaturated polyester, phenol, epoxy and the like,and as various kinds of additives that can be used in combination with amaterial described above as a main ingredient, exemplified are variouskinds of organic or inorganic reinforcing fibers such as a glass fiber,a carbon fiber, pulp, a synthetic resin fiber and the like; variouskinds of fillers such as talk, silica, mica, calcium carbonate, bariumsulfate, alumina and the like; colorants such as pigments, dyes and thelike; and various kinds of other additives such as a weather resistanceagent, an antistatic agent and the like.

No specific limitation is imposed on a color tone of a tooth crownportion forming material, but desirable is a slightly off-white color.No specific limitation is placed on a way of toning and it is onlyrequired that some of various kinds of known pigments and dyes areproperly combined so as to obtain a desired color tone. In the presentinvention, a color tone of a tooth crown portion forming material isadjusted so as to be preferably 15 or less and more preferably 10 orless in color difference ΔE*ab relative to a standard white color,thereby a good result of tooth shape measurement using laser light canbe obtained.

The term, a standard white color, means a color of a white color proofboard for a color difference meter manufactured according to JIS Z 8722and a color difference ΔE*ab in the present invention is defined as theaverage value of results of measurement on the surface of a test pieceformed so as to be flat obtained at any three sites therein using acolor difference meter manufactured according to JIS Z 8722.

In a case where such a tooth model for dentistry training of the presentinvention is manufactured, a manufacturing method is properly selectedaccording to a used material, however, for example, if a synthetic resinis used as a main ingredient, there can be employed known methods suchas a injection molding method, a press molding method and the like.

In order to form fine concavity and convexity on the surface of a toothcrown portion, the process for forming concavity and convexity may besimultaneously conducted during the course of forming a tooth model ormay be applied as a subsequent step after the forming. In order to formfine concavity and convexity on the surface of a tooth crown portionsimultaneously with the forming thereof, for example, in a case where araw material including a synthetic resin is used as a main componentthereof, it is only required that fine concavity and convexity is formedon the surface of a mold to thereby enable the reverse profile to betransferred on the surface of an obtained tooth. On the other hand, in acase where a profile with fine concavity and convexity is formed on thesurface of a tooth model in a post-treatment, there can be employedknown methods on the surface of a tooth model already formed such as ablasting treatment blasting fine powder, an etching treatment using achemical, a surface treatment with a sand paper or an abrasive powderand the like. Of various kinds of such known methods, preferably usedare a blasting treatment or an etching treatment forming a profile withfine concavity and convexity being applied on the surface of a moldedtooth model in a later step because of being capable of obtaining auniform concavity and convexity.

By the use of a method described above, a tooth model for dentistrytraining capable of correct shape measurement using laser light can beeasily obtained.

EXAMPLES

A material prepared by the method in which pulp was mixed into amelamine resin as a filler, and a pigment is added to the mixture toobtain a desired color tone was molded by injection molding to form atooth model for dentistry training having a shape shown in FIG. 1, and atreatment for forming fine concavity and convexity on the surface of atooth crown portion thereof is performed by using one of methods shownin respective examples. Measurement was conducted on completed toothmodels about a center line average roughness Ra, a light reflectance anda color difference ΔE*ab from a standard white color.

A center-line average roughness Ra was measured with a Surfcom 570A(manufactured by TOKYO SEIMITSU Co., Ltd.), a light reflectance wasmeasured with a spectrocolorimeter CM-3600d (manufactured by KonicaMinolta) and a color difference ΔE*ab from a standard white color wasmeasured with a color difference meter CR300 (manufactured by KonicaMinolta with a data processor DP300).

Shape measurement of the tooth models was conducted with a non-contact,high speed, three-dimensional shape measuring instrument VMS-100X(manufactured by Unisn INC.). Evaluation on results of measurement wasdetermined by the counts of data deficient portions occurring as holesin the results of measurement and a tooth model with no data deficientportion was evaluated as a good result. Measured values and shapemeasurement results on the tooth models are shown in Table 1.

Example 1

A material colored in a white color of 4.92 in a color difference ΔE*abfrom a standard white color was molded by injection molding, then, themolded product was subjected to a blasting treatment using aluminumoxide particles of the order in the range of from 10 to 80 μm inparticle diameter to obtain a tooth model with a surface having aprofile with concavity and convexity of a center-line average roughnessRa=0.19 μm and a light reflectance of 81.43% and thereafter, shapemeasurement was conducted on the tooth model. As a result, a good shapemeasurement result was achieved without any data deficient portion.

Example 2

A tooth model molded in a similar way to that adopted in Example 1 wassubjected to an etching treatment with a chemical to obtain the toothmodel with a surf ace having a profile with concavity and convexity of acenter-line average roughness Ra=1.01 μm and a light reflectance of82.74% and thereafter, shape measurement was conducted on the toothmodel. As a result, a good shape measurement result was achieved withoutany data deficient portion.

Comparative Example 1

A material similar to those used in Examples 1 and 2 were molded byinjection molding and thereafter, a fabricated tooth model was subjectedto a barrel polishing with an abrasive which is ceramic spheres of theorder of 1 mm to 2 mm in diameter to thereby obtain the tooth model witha surface having a profile with concavity and convexity of a center-lineaverage roughness Ra=0.09 μm and a light reflectance of 83.34% andthereafter, shape measurement was conducted on the tooth model. As aresult, two portions of data deficiency like holes in shape occurred,thereby not leading to a good measurement result.

Comparative Example 2

A material colored in a skin color of 17.09 in color difference ΔE*abfrom a standard white color was molded by injection molding, then, thefabricated tooth model was subjected to a blasting treatment usingaluminum oxide particles of the order in the range of from 10 to 80 μmin particle diameter to thereby obtain the tooth model with a surfacehaving a profile with concavity and convexity of a center-line averageroughness Ra=0.13 μm and a light reflectance of 62.88% and thereafter,shape measurement was conducted on the tooth model. As a result, fourportions of data deficiency like holes in shape occurred, thereby notleading to a good measurement result.

Comparative Example 3

A material similar to that used in Comparative Example 2 was molded byinjection molding and thereafter, a fabricated tooth model was subjectedto a barrel polishing with an abrasive which is ceramic spheres of theorder in the range of from 1 mm to 2 mm in diameter to thereby obtainthe tooth model with a surface having a profile with concavity andconvexity of a center-line average roughness Ra=0.08 μm and a lightreflectance of 65.75% and thereafter, shape measurement was conducted onthe tooth model. As a result, four portions of data deficiency likeholes in shape occurred, thereby not leading to a good measurementresult. TABLE 1 Measurement result as to tooth models described inExample 1, Example 2, and Comparative Examples 1 to 3 Result of shapemeasurement (portions of Color Center- data difference line averageLight deficiency in ΔE*ab roughness Ra reflectance shape) Example 1 4.920.19 μm 81.43% ∘ (0 portion) Example 2 4.92 1.01 μm 82.74% ∘ (0 portion)Comparative 4.92 0.09 μm 83.34% x (2 portions) Example 1 Comparative17.09 0.13 μm 62.88% x (4 portions) Example 2 Comparative 17.09 0.08 μm65.75% x (4 portions) Example 3

INDUSTRIAL APPLICABILITY

As seen from the results of the comparative experiments shown in Table1, in a case of a tooth model for dentistry training of the presentinvention, the shape of a tooth crown portion of a tooth model can becorrectly measured by a non-contact, high speed, three-dimensional shapemeasuring instrument and by using the shape measurement, results ofvarious kinds of a treatment practice and a preparation practice can becorrectly evaluated in the educational field.

1. A tooth model for dentistry training having a tooth crown portionformed as an imitation of the shape of a tooth, wherein at least thetooth crown portion is made of a tooth crown portion forming materialhaving non-transparency or semi-transparency, a center-line averageroughness Ra of the surface of the tooth crown portion is 0.1 μm or moreand less than 10 μm and a light reflectance of the surface of the toothcrown portion is 70% or higher for light of 700 nm in wavelength.
 2. Thetooth model for dentistry training according to claim 1, wherein a colordifference ΔE*ab from a standard white color of the tooth crown portionforming material is 15 or less.